This invention relates to gear oils for use in automotive transmissions and final drive axles. More particularly, this invention relates to gear oils that can meet GL-5 performance requirements while also meeting the L-60-1 test performance criteria of API MT-1.
Although a substantial number of gear oils have been produced having various needed properties where such gear oils are used, there exists a need for an additive or a combination of additives to provide an improved clean performing gear oil that can be used, e.g., in manual transmission oils and axle lubricants to reduce the deposits (i.e., build-up of sludge and other unwanted materials on metal surfaces such as carbon and varnish). While acceptable performance of the gear oil is a requirement, it is also highly desirable that the additive or additives be low in cost and easily produced.
Original equipment manufacturers desire lubricants having extended “drain capabilities” whereby their customers can operate the equipment for longer periods of time or for greater distances before draining the transmission or gear box of lubricant and replacing it with fresh lubricant. In view of the competitive situations in which they operate, lubricant manufacturers are also desirous of having the ability to provide low cost lubricants having these prolonged service capabilities. The invention realizes this cost savings through the omission of the costly ashless dispersants and dispersant viscosity index improvers.
Actual drainage periods utilized will depend, to a large extent, upon the type of severity of service and the design of the equipment. The present invention will allow under certain circumstances extended drainage intervals for many axle and transmission applications.
U.S. Pat. Nos. 5,176,840 and 5,225,093 to Campbell et al. disclose a gear oil additive package that includes: (1) an oil soluble succinimide and (2) a boronated or non-boronated carboxylic-type derivative composition produced by reacting a substituted succinic acylating agent with an amine and/or an alcohol. These patents also disclose that other components well known in the gear oil art can be added to the formulation. These other components include extreme pressure and anti-wear agents, defoamers, demulsifiers, antioxidants, dyes, pour point depressants and diluents. These references do not suggest or disclose an improved gear oil that is essentially devoid of carboxylic-type-type ashless dispersants such as the succinimides and Mannich base dispersants.
U.S. Pat. No. 5,354,484 discloses functional fluid compositions comprising (A) a major amount of an oil of lubricating viscosity, and a minor amount of (B-1) at least one soluble tertiary aliphatic primary amine salt of a substituted phosphoric acid composition, and (C) at least one soluble nitrogen-containing composition prepared by the reaction of a hydrocarbon-substituted succinic acid-producing compound with at least about one-half equivalent, per equivalent of acid producing compound, of an amine containing at least one hydrogen attached to a nitrogen atom. Preferably, the amine salts of the phosphoric acids utilized in the lubricating compositions of the present invention are derived from primary amines, and the soluble nitrogen-containing compositions (C) also contain boron.
U.S. Pat. No. 5,358,650 to Srinivasan et al. discloses an all-synthetic gear oil composition that comprises a base oil and a number of components such as organic sulfur-containing antiwear and/or extreme pressure agents, an organic phosphorus-containing anti-wear and/or extreme pressure agent, a copper corrosion inhibitor, a rust inhibitor, a foam inhibitor and an ashless dispersant such as the Mannich base dispersants or the polyamine succinimides.
U.S. Pat. No. 5,492,638 discloses gear oils comprising at least one overbased alkali or alkaline earth metal carboxylate, sulphonate or sulphurized phenate having a TBN of at least 200 in a gear oil which comprises an oil of lubricating viscosity at least 80% by volume of which is mineral oil, synthetic ester oil or a mixture thereof, Mannich base ashless dispersant; metal-free, sulphur-containing antiwear and/or extreme pressure agent; and metal-free, phosphorus-containing and nitrogen-containing antiwear and/or extreme pressure agent. The resultant gear oils exhibit excellent performance when used in synchromesh-based transmissions.
U.S. Pat. No. 5,691,283 discloses lubricant formulations for use in a motor vehicle, especially a heavy duty motor vehicle, having a transmission equipped with at least one cone-type synchronizer and an axle or differential gearing, the same lubricant is used for both such mechanisms. The lubricant has a viscosity grade level of from SAE 75W90 to SAE 85W140 and comprises base oil containing at least (i) Mannich base ashless dispersant; (ii) metal-free, sulphur-containing antiwear and/or extreme pressure agent; (iii) metal-free, phosphorus-containing and nitrogen-containing antiwear and/or extreme pressure agent; and (iv) overbased alkali or alkaline earth metal carboxylate, sulphonate or sulphurized phenate having a TBN of at least 145. The lubricant contains at most, if any, 100 ppm of metal as one or more metal-containing additive components other than (iv).
U.S. Pat. No. 5,763,372 discloses a clean gear boron-free gear additive employing a boron-free ashless dispersant, a sulfur source and a phosphorus source. More particularly, the preferred boron-free ashless dispersant is a hydrocarbyl succinimide. This additive composition when blended with a suitable base oil meets MT-1 and MIL-PRF-2105E requirements without the need for boron. MT-1 is a requirement for a clean gear manual transmission oil. MIL-PRF-2105E is a requirement for a rear axle oil.
U.S. Pat. No. 5,843,874 discloses a clean performing gear oil for use in transmission oils and axle lubricants. The gear oil having a Brookfield Viscosity at −12° C. ranging from about 1,000 to about 150,000 cP, comprises a base oil having a kinematic viscosity at 100° C. ranging from about 4.0 to about 41.0 cSt. Combined with the base oil is preferably a dispersant pour point depressant and/or a dispersant viscosity index improver. In a further embodiment, the gear oil is essentially devoid of carboxylic-type ashless dispersants (e.g., succinimide dispersants) and Mannich base dispersants, thus realizing a cost saving over conventional gear oils which are used as transmission and axle lubricants. Functionalized polymethylacrylates (PMA) are disclosed as agents that improve the properties of the gear oil and allow for the omission of conventional dispersants.
U.S. Pat. No. 5,942,470 discloses gear oils and gear oil additive concentrates of enhanced positraction performance. The gear oils comprise (i) at least one oil-soluble sulfur-containing extreme pressure or antiwear agent; (ii) at least one oil-soluble amine salt of a partial ester of an acid of phosphorus; and (iii) at least one oil-soluble succinimide. These compositions preferably contain one, more preferably two, and most preferably all three of the following additional components: (iv) at least one amine salt of a carboxylic acid; (v) at least one nitrogen-containing ashless dispersant; and (vi) at least one trihydrocarbyl ester of a pentavalent acid of phosphorus.
WO 00/01790 discloses a lubricating composition comprising a major amount of an oil of lubricating viscosity and (A) a di or trihydrocarbyl phosphite, (B) at least one reaction product of a di or trihydrocarbyl phosphite and sulfur or a source of sulfur; at least one di or trihydrocarbyl monothiophosphate; or salt thereof, and (C) a salt of a hydrocarbyl phosphoric acid ester. In one embodiment, the lubricant composition contains less than 0.1% phosphorus or less than about 0.75% borated dispersant.